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Reading your post I find myself understanding what you are saying... maybe. And that's my point. Communication is unclear. It's hard enough to follow this to
by Steeeve 9y ago
Reading your post I find myself understanding what you are saying... maybe. And that's my point. Communication is unclear.
It's hard enough to follow this topic for many people that want to keep updated. The fact that you have to spell out "please use SHA2-512/256, but not SHA2-512 and not SHA2-256" is mind-numbing.
"It's really SHA2-512/t where t has a value of 256 and that means that it's SHA2-512 truncated down which alleviates length extension attacks." Just typing that sentence gave me a headache and I have no real idea if it's right or not.
Adoption would be easy if communication was easy. As it is, it's a PITA to even have a short conversation on the subject.
- tptacek 9y agoI think you're confusing the SHA-2 hash core with a MAC derived from SHA-2. MACs and hashes aren't the same thing. You can build a MAC on a hash --- in fact, you can build a MAC on a hash that would be terribly insecure on its own, and some of those MACs are state-of-the art; see, for instance, all the polynomial MACs. That's what I'm trying to articulate. Hashes aren't MACs. This is partially my fault, for playing loose with SHA-2 512/256 vs "The Prefix MAC built on SHA-2 512/256". Again: I think we should just call that SHA-2-MAC. It's an unambiguous name that couldn't mean anything other than "truncated SHA-2 512 used as a prefix MAC".